Truck will not come out of 4x4 after plowing for a few hours.It has electric **** that controls 4x4.This has happened three times now weeks apart.Today I drove 20 miles to dealer then after getting to dealer it came out.It seems to be fine now.The dealer said nothing apparent wrong.They said it may be something to do with low voltage.There was a code for that that showed up eight days ago but not today.Thats when it happened last before today.It has been after plowing everytime.Which part is causeing this??